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On a model of piezoelectric beams including transverse interactions between different layers
No full textPaper N.1255
Extension of the Euler-Bernoulli model of piezoelectric laminates to include 3D effects via a mixed approach
No full textCorrections to the constitutive equations of piezoelectric laminated beams through a mixed variational approach
No full textChaotic and regular dynamics of a morphing shell with a vanishing-stiffness mode
No full textThin elastic shells are almost inextensible but easy to bend. In the presence of prestresses, geometric
frustrations can produce complex elastic energetic landscapes, which have been tailored for the design
of morphing structures with multiple stable equilibria or neutrally stable manifolds. We show that the
co-existence of stiff and floppy modes leads to unexploited dynamical features. We build a neutrally
stable cylindrical shell that under dynamical excitation alternates a chaotic behavior with a surprisingly
regular regimes with a continuous precession of the curvature axis at a constant speed. We explain the
experimental findings with a minimal model, showing how the intriguing dynamics is due to the subtle
coupling between the prestress, geometrical nonlinearity, material anisotropy and inertial effects.
Our results shed a new light on morphing structures dynamics and can be exploited in engineering
applications such as energy harvesting
Passive Electric Damping of Structural Vibrations through Distributed Piezoelectric Coupling: Critical Analysis
No full textVersailles (France
A neutrally stable shell in a Stokes flow: A rotational Taylor's sheet
Get PDFIn a seminal paper published in 1951, Taylor studied the interactions between a viscous fluid and an immersed flat sheet which is subjected to a travelling wave of transversal displacement. The net reaction of the fluid over the sheet turned out to be a force in the direction of the wave phase-speed. This effect is a key mechanism for the swimming of micro-organisms in viscous fluids. Here, we study the interaction between a viscous fluid and a special class of nonlinear morphing shells. We consider pre-stressed shells showing a onedimensional set of neutrally stable equilibria with almost cylindrical configurations. Their shape can be effectively controlled through embedded active materials, generating a large-amplitude shape-wave associated with precession of the axis of maximal curvature. We show that this shape-wave constitutes the rotational analogue of a Taylor's sheet, where the translational swimming velocity is replaced by an angular velocity. Despite the net force acting on the shell vanishes, the resultant torque does not. A similar mechanism can be used to manoeuver in viscous fluids
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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